Apparatus for recording sound on thin disks



May 1 1940- 1.. THOMPSON APPARATUS FOR RECORDING SOUND ON THIN DISKSFiled Dec. 15, 1938 TFI.

K AMPL 07m IIH INVENTOR Lincoln Thompson jaw.

ATTORNEY Patented May 14, 1940 PATENT OFFICE REESE? E APPARATUS FORRECORDING SOUND ON THIN DISKS Lincoln Thompson, Stamford, Conn.

Application December 15, 1938, Serial No. 245,944

2 Claims.

This invention relates to sound recording, and more particularly to anapparatus for recording sound on a thin disk record.

It has hitherto been considered impractical to 6 make sound recordingson a thin flexible disk due to the fact that the surface of said diskwould become permanently deformed and would warp so badly that it wouldnot play back with satisfaction, Even when relatively thick aluminumdisks 10 of the orderof .030" thickness (#20 gauge) were embossed withsound grooves in the conventional recording machines, it was found thatthe disks showed some warpage after recording. This was due largely tothe fact that the disk was mounted on a soft felt or yieldable rubberpad which permitted the heavy pressure of the embossing stylus (10 to 16ounces) to bend the disk record into dish form. With thinner disks, thisdishing or warping effect would naturally be greatly eg- 20 gravated.

By means of the present invention, the above and other disadvantageshave been overcome, and it has been found possible to emboss soundgrooves in an extremely thin flexible disk record v245 withoutappreciable warpage, using disks as thin as .006". This result has beenaccomplished by eliminating the soft felt or rubber pads previously usedas a frictional foundation for the disk record, and in placing therecord upon a solid 30 and rigid turntable or plate mounted on saidturntable. The tendency to produce warpage is still further reduced byemploying a lower embossing pressure on the stylus, whereby a moreshallow groove or sound track will be produced. 35 At the same time, inorder to drive the thin record without slippage, an interlockingconnection is made between the record and the spindle of the turntable,.as by providing a-square driving recess in the center of the record forfitting over 40 a similarly shaped section on said spindle.

By the use of this construction the thin record is supported rigidly sothat it cannot bend below the point of the embossing stylus, yetpermitting the latter to form a spiral groove in the surface 45 of therecord in a manner similar to the action of a plow.

One object of the present invention is to pro-- vide an apparatus bymeans ofwhich extremely thin disk records between .006" and .015" may 50be readily embossed with sound grooves on both faces, without producingsuilicient warpage as to interfere with the satisfactory playing backof.

the record.

A further object is to provide an apparatus by 65 means of which abendable semi-rigid record disk may be recorded which will not buckle upduring recording when positively driven by the center spindle andwithout the necessity of clamping the record on the turntable.

A still further object of this invention is to provide an apparatus forrecording on a thin semirigid metal disk which will be relativelyinexpensive to manufacture, simple in construction, ornamental inappearance, and very eflicient and durable in use.

With these and other objects in view, there have been illustrated ontheaccompanying drawing two forms of sound recording apparatus in whichthe invention may be conveniently embodied in practice.

In the drawing:

Fig. 1 illustrates partly diagrammatically the first form. of improvedsound recording apparatus embodying the present invention.

Fig. 2 is a top plan view of the thin disk record as it appears wheninterlocked with the turntable spindle, and with the embossing stylus inoperating position,

Fig. 3 is an enlarged side view, partly in section, of the thin-diskrecord turntable and embossing stylus shown'in Fig. 2, taken on the line3--3 of Fig. 2.

Fig. 4 is a greatly enlarged sectional view of the disk record,turntable and stylus in operating position.

Fig. 5 illustrates a fragmentary side view of a modified form of theinvention employing a rigid record supporting plate resting on the usualturntable felt cushion.

Referring now to the drawing wherein like reference numerals denote likeparts throughout the several views, the numeral l designates a turntablewhich is adapted to be rotated by an electric motor Ii in theconventional manner. The motor H is adapted to be energized by beingconnected to a source of electrical energy through main line conductorsl2 and It, a plug ll, conductors l and. I6, and a switch ll.

The sound grooves are adapted to be embossed in the record by means ofan electrically actuated recording head It arranged to swing over theturntable l0 and being driven in this swinging movement by power drivenmechanism, not shown. A suitable mechanism for this purpose wasdisclosed in my prior patent, No. 2,133,596, dated October 18, 1938. Thesound vibrations received by the apparatus are reproduced in the form ofa spiral groove in the disk record 24 by means of an embossing" stylusl9 carried by the recording head it, the latter being responsive to n lerical circuit which includes a microphone p on s'that 20, a. pair ofconductors 2|, a vacuum tube ampliwhen recording with either form ofapparatus fler 22, and apair of conductors 23. The recordhereindisclosed, the stylus l9 will emboss or ing head 18 is of a conventionaltype, and is plow a sound groove 25 in the surface of either 5 adaptedto rest upon the surface of a disk record side of the disk record 24without appreciable 6 24 with a pressure of about four ounces. warping.

The disk record 24 is preferably made from a In operation, the stylus l9forces up a. pair of thin flexible metal, such as sheet aluminum,havlateral ribs 3! and 32, which define the side ing a thickness of lessthan .015", and preferably borders of the sound groove and mater alllire- 1; a t inforce the stiflness of the record 10 s'iredj he blank ds ry 4,; may have a ring-shapedmarking areal 33"etched upon its surfacewithin the sound grooves for permitting the user to make any desiredindicia or memorandagtheregn yvith a pencil. Three rectangular l5 apedmarking portions 34, 35 and 36 may also etched on the record forreceiving any other desired 'ndicia pertaining to the soundsrecordedduring handling or recording Foraexample ylf I a disk .006" inthickness is use round that if desired, the op- 20 erator =may writedirectly across the sound .--J h; :a-: at smogthhe a i a 7'28sthusgnreveniz n h whoss n z-ltr ci I a a ation,

In the modified form ofthe invention shown i Fig.:;5, insteadi'of-'supportin'g'theiidislc record 24:

'; directlyioniithe turntable'zitop 128,?iascin :the:first.-3., arm loateda vew aidreq d n hav n r .form; aismooth rigidplate 29iszemployedzand is cutting head for indenting 1aterally;.undu1at:ing

1 1 adapted ito restupon the xusualielt cushion pad rchelical:groovesgin saidrecord-withoutsubstantial whichi-is glued-ror cementedztotheqturntable :1 s-

a g w, L H

